Date of Award

Summer 2022

Document Type

Open Access Thesis


Mechanical Engineering

First Advisor

Lingyu Yu


Effective non-destructive evaluation (NDE) inspection system and methods are highly desired in a broad range of engineering applications including thin metal structure thickness evaluation. Ultrasonic guided waves in thin-walled structures, namely Lamb waves, have gained popularity as a NDE method. By using the ultrasonic waves in conjunction with high spatial resolution multidimensional wavefield measurements, thickness evaluations for thin metals can be achieved. This thesis explores the configuration and application of a fully noncontact ultrasonic Lamb wave NDE system for thickness characterization and evaluation of very thin metal plates. We have tested the actuation and sensing of Lamb waves for thickness characterization in thin aluminum plates and have studied the application on thin materials including aluminum foils and nuclear grade Zircaloy cladding material. The non-contact system consists of a pulsed laser (PL) working in the thermoelastic regime to excite Lamb waves and scanning laser Doppler vibrometer (SLDV) for sensing the waves and providing high resolution multidimensional wavefield signals for evaluation. To excite high frequency Lamb waves, efforts are made on sensing, actuation parameters, and surface enhancement exploration. The results show that excited Lamb waves can reach frequencies greater than 1000 kHz in plates thinner than 1 mm and are effective in thickness measurement. Additionally, a preliminary study on carbon fiber reinforced polymer (CFRP) composite is conducted to explore the potential for applications in other fields.


© 2022, Elsa Z. Compton